Ghanima's favorite weapon is her crysknife, but she's also pretty deadly with her kama, tambo, bo, and any sort of knife or short-sword. She's also killed people in book-canon with a blowdart.

In reality, if you hand her a weapon, she can probably use it. She has full access to her Other Memory (see the Inherent Abilities thread), so if it's something one of her ancestors would have used, she can use it too. Maybe not at a mastery level the first few times, but she'd still be very good.